|Publication number||US7379826 B2|
|Application number||US 11/504,486|
|Publication date||May 27, 2008|
|Filing date||Aug 15, 2006|
|Priority date||Feb 3, 2003|
|Also published as||EP1597569A2, US6957154, US7092826, US20040152250, US20050234658, US20060276976, WO2004070355A2, WO2004070355A3, WO2004070355B1|
|Publication number||11504486, 504486, US 7379826 B2, US 7379826B2, US-B2-7379826, US7379826 B2, US7379826B2|
|Inventors||M. Brandon Steele, Jeffrey Alan Hawthorne|
|Original Assignee||Qcept Technologies, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (69), Non-Patent Citations (12), Referenced by (3), Classifications (8), Legal Events (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a continuation of U.S. application Ser. No. 11/156,088, filed Jun. 17, 2005, now U.S. Pat. No. 7,092,826 which is a continuation of U.S. application Ser. No. 10/631,469, filed Jul. 29, 2003, now U.S. Pat. No. 6,957,154 which claims priority to U.S. application Ser. No. 60/444,504, filed on Feb. 3, 2003 all three of which are incorporated herein by reference.
The present invention is directed to a method and system for inspection of semiconductor wafers and other materials. More particularly, the invention is directed to a method and system for characterization of microscopic and macroscopic defects through imaging and visualization of contact potential difference topology on a wafer or material surface through use of a non-vibrating contact potential difference (hereinafter NVCPD) sensor.
The multi-billion dollar global market for semiconductor defect management is growing both in absolute terms and as a percentage of semiconductor capital equipment investment. In general, there are two factors that determine the economics of a semiconductor fabrication facility at a given utilization level, namely throughput and yield. As complex new technologies such as 300 mm wafers, copper interconnects, and reduced feature (circuit) sizes drive the margin of error in fabrication ever lower, new inspection technologies are critical to keep yields high and bottom-line economics attractive. Detection and elimination of chemical contamination and other types of defects is a constant concern for semiconductor manufacturers and equipment suppliers. Contamination can arise from use of processing chemicals, processing equipment and poor handling techniques. Contaminants can include for example metals, carbon and organic compounds. Other types of defects can result from a wide range of causes, including flaws in the semiconductor crystal, improper processing, improper handling, and defective materials. In addition, many cleaning steps are required in semiconductor wafer fabrication. Each step is time consuming and requires expensive chemicals that may require special disposal procedures. Existing methods for monitoring or controlling these processes are expensive and time consuming. As a result, wafers are often cleaned for a longer period of time and using more chemicals than are required.
Defect detection and characterization systems can be divided into in-line and off-line systems. “In-line” refers to inspection and measurement that takes place inside the clean room where wafers are processed. “Off-line” refers to analysis that takes place outside of the wafer processing clean room, often in a laboratory or separate clean room that is located some distance from the manufacturing area. In addition, many of these analytical techniques are destructive, which requires either the sacrifice of a production wafer or the use of expensive “monitor” wafers for analysis. In-line inspection and measurement is crucial for rapidly identifying and correcting problems that may occur periodically in the manufacturing process. A typical wafer can undergo over 500 individual process steps and require weeks to complete. Each wafer can have a finished product value of up to $100,000. Because the number of steps, and period of time, involved in wafer fabrication are so large, a lot of work in process can exist at any point in time. It is critical that process-related defects be found and corrected immediately before a large number (and dollar value) of wafers are affected.
Many types of defects and contamination are not detectable using existing in-line tools, and these are typically detected and analyzed using expensive and time-consuming “off line” techniques (described below) such as Total Reflectance X-ray Fluorescence (TXRF), Vapor Phase Decomposition Inductively Coupled Plasma-Mass Spectrometry (VPD ICP-MS) or Secondary Ion Mass Spectrometry (SIMS). Since these techniques are used off-line (outside of the clean room used to process wafers) and usually occur hours, or even days, after the process step that has caused the contamination, their value is significantly limited.
A brief description of some well known techniques for wafer inspection and chemical contamination detection are presented in Table 1. This list is not in any sense exhaustive as there are a very large number of techniques that are used for some type of semiconductor analysis or characterization.
X-rays irradiate the wafer within
the critical angle for total
external reflectance, causing
surface atoms to fluoresce.
Optical images are acquired and
automatically analyzed for
detection of large defects.
Wafer surface is illuminated
with laser spots and the angle
and/or polarization of reflected
light is analyzed to detect and
Wafers “scanned” with a
drop of HF that is analyzed using
Ion beam sputters the wafer
surface creating secondary ions
that are analyzed in a mass
Table 2 summarizes some major advantages and disadvantages of each technique. In general, off-line detection techniques are extremely sensitive to tiny amounts of contamination; but are slow, expensive and complex to operate. Some have limited, or no, imaging or surface mapping capability, or are destructive in nature. In-line techniques are much faster, non-destructive and provide defect mapping, but have limited chemical contamination detection or analysis capability.
Slow (>1 hour/wafer)
Detects a wide range of
Imaging of wafer surface
Only detects particles -
Relatively low cost
Detects very small
Imaging of water surface
Able to identify wide
range of contaminants
Only works on bare
Detects a wide range
In general, existing in-line wafer inspection tools operate at production speeds and generate images of the wafer surface that are processed to identify and locate defects. These techniques, however, are as mentioned above very limited in their ability to detect chemical contamination. Laser backscattering systems are limited to detecting particles down to sub-micron sizes, and optical microscopy systems can only detect chemical contamination that results in a visible stain or residue. Both techniques lack the ability to identify or classify the chemical composition of the particle or contamination. Off-line laboratory techniques are used to qualify the cleanliness of new processes and equipment, or to analyze defects detected by in-line equipment or as part of failure analysis. A critical need therefore exists for a fast, inexpensive and effective means of detecting, locating and classifying relatively small quantities of chemical contamination on production wafers.
It is therefore an object of the invention to provide an improved method and system for inspection of surfaces of materials, such as semiconductor wafers.
It is an additional object of the invention to provide an improved method and system for providing images of surface defects on an semiconductor wafer.
It is yet another object of the invention to provide an improved method and system for identifying different classes of semiconductor wafer surface defects by pattern recognition.
It is still a further object of the invention to provide an improved method and system for classifying categories of surface defects on semiconductor wafers, including without limitation surface defect states, electrostatic field variations, oxide states and chemical contamination.
It is also an additional object of the invention to provide an improved method and system for sensing electrostatic fields arising from semiconductor wafer surface defects.
It is yet another object of the invention to provide an improved method and system for detecting the presence of thin dielectric films on surfaces of semiconductor wafers and to detect film defects such as pinholes, bubbles, delaminations, or contamination under the film.
It is a further object of the invention to provide an improved method and system to sense variations in oxide states on semiconductor wafer surfaces.
It is also a further object of the invention to provide an improved method and system to classify particulate contaminants on semiconductor wafers identified initially by optical inspection systems.
It is yet a further object of the invention to provide an improved method and system for detecting variations in dopant concentration of semiconductor wafers.
It is another object of the invention to provide an improved method and system for use of an NVCPD sensor to inspect the surface quality of semiconductor wafers.
It is still another object of the invention to provide an improved method and system of NVCPD sensors in combination with other inspection systems for evaluating semiconductor wafer surface properties.
It is a further object of the invention to provide an improved method and system for producing topological images of differing contact potential characteristic of defects on a semiconductor wafer.
It is also an object of the invention to provide an improved method and system for rapidly scanning the surface of a semiconductor wafer to identify sub-microscopic, microscopic and macroscopic surface defects characterized by potential field disturbances on the wafer surface.
It is also an object of the invention to provide an improved method and system for detecting the cleanliness of a semiconductor wafer to determine if a cleaning process has eliminated all contaminants and to avoid the time and expense of cleaning wafers for longer than is necessary to remove contaminants.
In each case described above, wafer surface can refer to the front-side (patterned side) of the wafer, back-side (unpatterned side) of the wafer, or the edge of the wafer.
Other objects, features and advantages of the present invention will be readily apparent from the following description of the preferred embodiment thereof, taken in conjunction with the accompanying drawings described below.
The preferred embodiment of the invention is directed to an improved use of an NVCPD sensor. In particular,
where ∈o is the permittivity of free space, ∈r, is the relative dielectric constant, A is the area of the probe tip, d is the distance between the sensor tip 13 and the wafer 15, Φ is the work function of the respective surface, and e is the charge on an electron. The V term can also be described as a difference in surface potentials between the NVCPD sensor 12 and the wafer 15. In addition the surface potentials on the wafer surface 16 can vary due to defects. The overall surface potential is related to the underlying materials work function but it can also be affected by adsorbed layers of material on the wafer surface 16. Even sub mono-layers of materials are known to significantly affect the surface potential.
term is related to changes in work function on the wafer surface 16. It can be seen that the magnitude of this term is related to the relative changes in work function on the wafer surface 16 and relative speed at which the NVCPD sensor 12 is moved over the wafer surface 16. An illustration of the signal generated from this can be seen in
Many defects can present themselves as variations in the wafer work function or the overall surface potential. For instance variation in semiconductor dopant concentrations in the wafer 15 will cause varying characteristic work functions. In addition other materials that could diffuse into the wafer 15 such as copper will cause variations in work function. Within the semiconductor material itself, mechanical phenomena such as dislocation pile-ups, cracks, and scratches generate local stresses which will change the local work function. In addition, adsorbed layers of atomic or molecular contaminants even at the sub monolayer level will generate appreciable surface potential variations. Particles deposited on the wafer 16 with a surface potential different than the surrounding wafer material will also create a signal. Layers of chemicals commonly used in the wafer fabrication process will affect the surface potential of the wafer. For instance residual CMP slurry or photo-resist would cause local variations in surface potential detectable by the NVCPD sensor 12.
term is related to changes in gap between the NVCPD sensor 12 and the wafer 15 or variations in the relative dielectric constant. Geometrical imperfections in the wafer surface 16 or particles on the wafer surface 16 would manifest themselves in this component. Also because of its differential nature the magnitude of this component would also increase as the relative speed of the NVCPD sensor 12 is increased.
Many classes of wafer defects would appear as geometrical changes in the wafer surface 16. In the wafer 15 itself surface cracks, scratches, etched trenches, etc. would be examples of this. In addition particles deposited on the wafer 15 would also present themselves as a local change in the distance to the probe sensor tip 13.
Variations of dielectric films on the wafer 15 can also be detected. An example would be detecting variations in the oxide state grown on the silicon substrate (i.e. SiO, SiO2, SiO3, SiO4). In addition variations in dielectric of other non-conducting materials commonly deposited on the wafer could be detected.
It should also be noted that many features could present themselves as combinations of geometrical changes and chemical changes. For instance a particle deposited on the wafer 15 of differing material than the underlying wafer 15. Also a crack in the surface would also induce stresses that would cause variations in local work function.
As shown in more detail in
The images generated were subsequently processed to automatically locate defects. The idea behind this process was to locate areas of high variability. An ideal surface would exhibit a flat signal but a wafer surface with defects would exhibit some variability in the signal. To locate areas with defects the data was broken up in to small areas of known location. The standard deviation of the signal within these areas was determined. Areas with defects showed a higher standard deviation, and these results can be seen in
More generally, a defect can be identified by one or more of the following:
1. Process the data to look for a voltage or change in voltage (or pattern of voltages or changes in voltages) that exceeds some user-defined value (threshold).
2. Compare the data to a known pattern that represents a defect via some form of correlation or template matching.
3. Convert the spatial data to the frequency domain and then identify peaks in the frequency domain that represent defects with unique spatial characteristics.
These techniques can also be combined with other techniques to yield analytical results. The signal may also be preprocessed to facilitate defect detection, such as, for example:
1. Since the signal is differential, it can be integrated over some distance to produce voltages that represent relative CPD's over the surface of the wafer 15.
2. If the wafer 15 is “patterned”, then this known pattern can be removed from the data prior to processing. This would likely be accomplished through some variation of image or signal subtraction in either the space or frequency domains.
3. The signal would likely be processed with some form of frequency filtering to remove high or low frequencies depending on the size, shape and other characteristics of the expected defects.
4. The signal could be processed to remove features of a certain size by doing what is called “morphological processing.”
The following non-limiting example describes methods of preparation of test wafers and sensing characteristic images for identifying certain defect states, chemical states, electrostatic states and mechanical features present on a semiconductor wafer surface.
Sample wafers can be created by dip coating the wafer 15 in solutions that contain known concentrations of contaminants. Part of this example describes metal contaminants such as Cu and Fe, although any manner of chemical contaminants can be applied in this way. The wafer 15 described is either a 100 mm or 150 mm wafer, although these examples apply to any size wafer. The wafer surface 16 is prepared by dipping in HF to remove oxides. The wafer 15 is then cleaned and partially dipped in the metal contaminant solution. The amount of solution remaining on the wafer 15, and the resulting concentration of contaminant on the wafer surface 16, is controlled by selecting dip coating parameters such as the extraction rate.
Partial dipping of the test wafer 15 is preferred to create a transition from clean to contaminated areas. Because the NVCPD signal is differential, the NVCPD sensor 12 detects changes on the wafer surface 16, as opposed to an absolute value relating to surface condition. This aspect of NVCPD sensors 12 is offset by the ability to rapidly image and detect localized contamination anywhere on the surface of the wafer 15.
After preparation, each test wafer 15 can be, if necessary, analyzed using an appropriate combination of XPS, Auger and RBS (or other well known surface analysis methods) techniques to determine actual contaminant concentrations in the dipped areas of the wafer 15. Each step involved in the sample wafer preparation process is shown in
After each sample wafer 15 is created, it can be imaged using a radially scanning NVCPD imaging system 10 constructed in accordance with the invention. As described before,
The imaging system 10 has been used for a variety of surface analysis experiments.
The second set of images in
While preferred embodiments of the invention have been shown and described, it will be clear to those skilled in the art that various changes and modifications can be made without departing from the invention in its broader aspects as set forth in the claims provided hereinafter.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US4166974||Jan 23, 1978||Sep 4, 1979||The United States Of America As Represented By The Secretary Of The Navy||Apparatus and method for measuring capacitive energy|
|US4295092||Nov 3, 1978||Oct 13, 1981||Koa Oil Company, Limited||Apparatus for and method of detecting and measuring corrosion damage in pipe|
|US4481616||Sep 30, 1981||Nov 6, 1984||Rca Corporation||Scanning capacitance microscope|
|US4973910||Feb 21, 1989||Nov 27, 1990||Wilson Mahlon S||Surface potential analyzer|
|US5087533||Jan 7, 1991||Feb 11, 1992||Brown Paul M||Contact potential difference cell|
|US5136247||Jan 18, 1991||Aug 4, 1992||Hansen Wilford N||Apparatus and methods for calibrated work function measurements|
|US5214389||Jan 6, 1992||May 25, 1993||Motorola, Inc.||Multi-dimensional high-resolution probe for semiconductor measurements including piezoelectric transducer arrangement for controlling probe position|
|US5217907||Jan 28, 1992||Jun 8, 1993||National Semiconductor Corporation||Array spreading resistance probe (ASRP) method for profile extraction from semiconductor chips of cellular construction|
|US5218362||Jul 2, 1992||Jun 8, 1993||National Semiconductor Corporation||Multistep analog-to-digital converter with embedded correction data memory for trimming resistor ladders|
|US5270664||Oct 2, 1991||Dec 14, 1993||Renishaw, Plc||Probe for measuring surface roughness by sensing fringe field capacitance effects|
|US5272443||Apr 22, 1992||Dec 21, 1993||Aluminum Company Of America||Chatter and profile measuring using capacitor sensors|
|US5278407||Apr 24, 1992||Jan 11, 1994||Hitachi, Ltd.||Secondary-ion mass spectrometry apparatus using field limiting method|
|US5293131||Sep 4, 1992||Mar 8, 1994||Measurement Systems, Inc.||Capacitive probe for bore measurement|
|US5315259||May 26, 1992||May 24, 1994||Universities Research Association, Inc.||Omnidirectional capacitive probe for gauge of having a sensing tip formed as a substantially complete sphere|
|US5369370||Jun 12, 1991||Nov 29, 1994||Max-Planck-Institut Fuer Eisenforschung Gmbh||Method and apparatus for the measurement of the corrosion potential between a coated metal surface and a reference electrode|
|US5381101||Dec 2, 1992||Jan 10, 1995||The Board Of Trustees Of The Leland Stanford Junior University||System and method of measuring high-speed electrical waveforms using force microscopy and offset sampling frequencies|
|US5460684||Dec 3, 1993||Oct 24, 1995||Tokyo Electron Limited||Stage having electrostatic chuck and plasma processing apparatus using same|
|US5517123||Aug 26, 1994||May 14, 1996||Analog Devices, Inc.||High sensitivity integrated micromechanical electrostatic potential sensor|
|US5546477||Mar 30, 1993||Aug 13, 1996||Klics, Inc.||Data compression and decompression|
|US5583443||Jun 7, 1995||Dec 10, 1996||Renishaw Plc||Calibration of capacitance probe|
|US5723980||Jun 7, 1995||Mar 3, 1998||Aerogage Corporation||Clearance measurement system|
|US5723981||Jun 25, 1996||Mar 3, 1998||Imec Vzw||Method for measuring the electrical potential in a semiconductor element|
|US5773989||Jul 14, 1995||Jun 30, 1998||University Of South Florida||Measurement of the mobile ion concentration in the oxide layer of a semiconductor wafer|
|US5789360 *||Jan 2, 1997||Aug 4, 1998||Samsung Electronics Co., Ltd.||Cleaning solution for use on a semiconductor wafer following chemical-mechanical polishing of the wafer and method for using same|
|US5974869||Nov 14, 1997||Nov 2, 1999||Georgia Tech Research Corp.||Non-vibrating capacitance probe for wear monitoring|
|US5977788||Jul 11, 1997||Nov 2, 1999||Lagowski; Jacek||Elevated temperature measurement of the minority carrier lifetime in the depletion layer of a semiconductor wafer|
|US6011404||Jul 3, 1997||Jan 4, 2000||Lucent Technologies Inc.||System and method for determining near--surface lifetimes and the tunneling field of a dielectric in a semiconductor|
|US6037797||Jul 11, 1997||Mar 14, 2000||Semiconductor Diagnostics, Inc.||Measurement of the interface trap charge in an oxide semiconductor layer interface|
|US6091248||Mar 2, 1998||Jul 18, 2000||Imec Vzw||Method for measuring the electrical potential in a semiconductor element|
|US6094971||Sep 24, 1997||Aug 1, 2000||Texas Instruments Incorporated||Scanning-probe microscope including non-optical means for detecting normal tip-sample interactions|
|US6097196||Apr 23, 1997||Aug 1, 2000||Verkuil; Roger L.||Non-contact tunnelling field measurement for a semiconductor oxide layer|
|US6114865||Apr 21, 1999||Sep 5, 2000||Semiconductor Diagnostics, Inc.||Device for electrically contacting a floating semiconductor wafer having an insulating film|
|US6127289||Sep 5, 1997||Oct 3, 2000||Lucent Technologies, Inc.||Method for treating semiconductor wafers with corona charge and devices using corona charging|
|US6139759||Feb 23, 1999||Oct 31, 2000||International Business Machines Corporation||Method of manufacturing silicided silicon microtips for scanning probe microscopy|
|US6198300||Nov 8, 1999||Mar 6, 2001||International Business Machines Corporation||Silicided silicon microtips for scanning probe microscopy|
|US6201401||Nov 23, 1998||Mar 13, 2001||Imec||Method for measuring the electrical potential in a semiconductor element|
|US6232134||Jan 24, 2000||May 15, 2001||Motorola Inc.||Method and apparatus for monitoring wafer characteristics and/or semiconductor processing consistency using wafer charge distribution measurements|
|US6255128||Aug 6, 1998||Jul 3, 2001||Lucent Technologies Inc.||Non-contact method for determining the presence of a contaminant in a semiconductor device|
|US6265890||Aug 26, 1999||Jul 24, 2001||Lucent Technologies Inc.||In-line non-contact depletion capacitance measurement method and apparatus|
|US6517669||Feb 26, 1999||Feb 11, 2003||Micron Technology, Inc.||Apparatus and method of detecting endpoint of a dielectric etch|
|US6520839||Mar 2, 2000||Feb 18, 2003||Speedfam-Ipec Corporation||Load and unload station for semiconductor wafers|
|US6538462||Nov 30, 1999||Mar 25, 2003||Semiconductor Diagnostics, Inc.||Method for measuring stress induced leakage current and gate dielectric integrity using corona discharge|
|US6546814||Mar 13, 1999||Apr 15, 2003||Textron Systems Corporation||Method and apparatus for estimating torque in rotating machinery|
|US6551972||Mar 24, 1998||Apr 22, 2003||Merck Patent Gesellschaft||Solutions for cleaning silicon semiconductors or silicon oxides|
|US6590645 *||May 4, 2000||Jul 8, 2003||Kla-Tencor Corporation||System and methods for classifying anomalies of sample surfaces|
|US6597193||Mar 16, 2001||Jul 22, 2003||Semiconductor Diagnostics, Inc.||Steady state method for measuring the thickness and the capacitance of ultra thin dielectric in the presence of substantial leakage current|
|US6664546||Feb 10, 2000||Dec 16, 2003||Kla-Tencor||In-situ probe for optimizing electron beam inspection and metrology based on surface potential|
|US6664800||Jan 8, 2001||Dec 16, 2003||Agere Systems Inc.||Non-contact method for determining quality of semiconductor dielectrics|
|US6679117||Feb 7, 2001||Jan 20, 2004||Georgia Tech Research Corporation||Ionization contact potential difference gyroscope|
|US6680621||May 8, 2001||Jan 20, 2004||Semiconductor Diagnostics, Inc.||Steady state method for measuring the thickness and the capacitance of ultra thin dielectric in the presence of substantial leakage current|
|US6711952||Oct 5, 2001||Mar 30, 2004||General Electric Company||Method and system for monitoring bearings|
|US6717413||Apr 21, 2000||Apr 6, 2004||Georgia Tech Research Corporation||Contact potential difference ionization detector|
|US6771091||Sep 24, 2002||Aug 3, 2004||Semiconductor Diagnostics, Inc.||Method and system for elevated temperature measurement with probes designed for room temperature measurement|
|US6791310||Jul 26, 2002||Sep 14, 2004||Therma-Wave, Inc.||Systems and methods for improved metrology using combined optical and electrical measurements|
|US6803241||Jan 9, 2003||Oct 12, 2004||Samsung Electronics Co., Ltd.||Method of monitoring contact hole of integrated circuit using corona charges|
|US6849505||Sep 12, 2002||Feb 1, 2005||Hynix Semiconductor Inc.||Semiconductor device and method for fabricating the same|
|US6858089||Dec 23, 2003||Feb 22, 2005||Paul P. Castrucci||Apparatus and method for semiconductor wafer cleaning|
|US6929531||Sep 19, 2002||Aug 16, 2005||Lam Research Corporation||System and method for metal residue detection and mapping within a multi-step sequence|
|US7019654||Feb 27, 2002||Mar 28, 2006||Georgia Tech Research Corporation||Contact potential difference sensor to monitor oil properties|
|US7084661||May 18, 2001||Aug 1, 2006||Sensorchem International Corporation||Scanning kelvin microprobe system and process for analyzing a surface|
|US20030139838||Jan 15, 2003||Jul 24, 2003||Marella Paul Frank||Systems and methods for closed loop defect reduction|
|US20030164942||Dec 7, 2000||Sep 4, 2003||Kunihiko Take||Semiconductor wafer examination system|
|US20040029131||May 18, 2001||Feb 12, 2004||Michael Thompson||Scanning kelvinmicroprobe system and process for biomolecule microassay|
|US20040105093||Nov 28, 2003||Jun 3, 2004||Akira Hamamatsu||Inspection method and inspection apparatus|
|DD297509A5||Title not available|
|EP1039277A1||Mar 14, 2000||Sep 27, 2000||Meritor Heavy Vehicle Systems, LLC||Torsional vibration monitoring system|
|EP1304463A1||Oct 4, 2002||Apr 23, 2003||General Electric Company||Method and system for monitoring bearings|
|WO2001090730A2||May 18, 2001||Nov 29, 2001||Sensorchem International Corporation||Scanning kelvin microprobe system and process for analyzing a surface|
|WO2004070355A2||Feb 3, 2004||Aug 19, 2004||Qcept Technologies Inc.||Wafer inspection using a nonvibrating contact potential difference probe (nonvibrating kelvin probe)|
|1||B Scruton and B.H. Blott, A High Resolution Probe for Scanning Electrostatic Potential Profiles Across Surfaces; Journal of Physics E: Scientific Instruments (May 1973), pp. 472-474; vol. 6, No. 5, Printed in Great Britian.|
|2||Baumgartner H et al: "Micro Kelvin probe for local work-function measurements", Review of Scientific Instrumetns, May 1988, USA; vol. 59, No. 5, pp. 802-805, XP002292442, ISSN: 0034-6748 (abstract; fig. 4, chapter "V. Results").|
|3||Castaldini A et al: "Scanning Kelvin probe and surface photovoltage analysis of multicrystalline silicon", Materials Science and Engineering B., Elsevier Sequoia, Lausanne, CH; vol. 91-92, Apr. 30, 2002, pp. 234-238, XP004355534, ISSN: 0921-5107 (chapters "2.2 Scanning Kelvin probe: and 4.2 Scanning Kelvin probe analyses").|
|4||Castaldini A et al: "Surface analyses of polycrystalline and Cz-Si wafers", Solar Energy Materials and Solar Cells, Elsevier Science Publishers, Amsterdam, NL; vol. 72, No. 1-4, Apr. 2002, pp. 425-432, XP004339790, ISSN: 0927-0248 (whole document).|
|5||Danyluk S: "Non-vibrating contact potential imaging for semiconductor fabrication", Semicon West 2003, 'Online!, Jul. 14, 2003, pp. 1-15, XP002292443, retrieved from the internet: ,URL:http://dom.semi.org/web/wFiles.nsf/Lookup/TIS18<SUB>-</SUB>QceptTechnologiesInc/$file/TIS18%20QceptTechnologiesInc.Alternate.pdf. retrieved on Aug. 13, 2004 (whole document).|
|6||Korach C S et al: "Measurement of perfluoropolyether lubricant thickness on a magnetic disk surface", Applied Physics Letters, American Institute of Physics, New York, NY, US; vol. 79, No. 5, Jul. 30, 2001, pp. 698-700, XP012029958, ISSN: 0003-6951 (p. 699, left column; fig. 2).|
|7||Lagel B et al: "A novel detection system for defects and chemical contamination in semiconductors based upon the scanning Kelvin probe", 14<SUP>th </SUP>International Vacuum Congress (IVC-14). 10<SUP>th </SUP>International Conference on Solid Surfaces (ICS-10). 5<SUP>th </SUP>International Conference on Nanometre-Scale Science and Technology (NANO-5). 10<SUP>th </SUP>International Conference on Quantitative Surfaces Analysis; vol. 433-435, pp. 622-626, XP002292441, Surface Science, Aug. 2, 1999, Elsevier, NL, ISSN: 003906028 (whole document).|
|8||Moorman, M. et al., "A Novel, Micro-Contact Potential Difference Probe," Sensors and Actuators B, Elsevier Sequoia S.A., Lausanne, CH, vol. 94, No. 1.|
|9||Reid, Jr., Lennox Errol, "Surface Characterization of Hard Disks Using Non-Contact Work Function Capacitance Probe," A Thesis Presented to the Academic Faculty in Partial Fulfillment of the Requirements for the Degree of Master of Science in Mechanical Engineering, Georgia Institute of Technology, Jun. 1986.|
|10||Ren J et al: "Scanning Kelvin Microscope: a new method for surface investigations" 8. Arbeitstatgung Angewandte Oberflachenanalytik 'AOFA 8' ('Applied Surface Analysis'), Kaiserslautern, DE, Sep. 5-8, 1994; vol. 353, No. 3-4, pp. 303-306, XP009035181, Fresenius' Jounal of Analytical Chemistry, Oct. 1995, Springer-Verlag, DE, ISSN: 0937-0633 (p. 304, right column; fig. 1).|
|11||Yang Y et al: "Kelvin probe study on the perfluoropolyether film on metals", Tribology Letters, 2001, Kluwer Academic/Plenum Publishers, USA, vol. 10, No. 4, pp. 211-216, XP009035197, ISSN: 1023-8883 (p. 211-p. 212).|
|12||Yano D et al: "Nonvibrating contact potential difference probe measurement of a nanometer-scale lubricant on a hard disk", Journal of Tribology, American Society of Mechanical Engineers, New York, NY US; vol. 121, No. 4, Oct. 1999, pp. 980-983, XP008031092, ISSN: 0742-4787 (pp. 980-981, fig. 4, first ref. on p. 983).|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US8731274 *||Apr 10, 2011||May 20, 2014||Camtek Ltd.||Method and system for wafer registration|
|US20080319568 *||Jun 22, 2007||Dec 25, 2008||International Business Machines Corporation||Method and system for creating array defect paretos using electrical overlay of bitfail maps, photo limited yield, yield, and auto pattern recognition code data|
|US20120195490 *||Apr 10, 2011||Aug 2, 2012||Eldad Langmans||Method and system for wafer registration|
|International Classification||G01N33/00, G01N27/00, G01B5/28|
|Cooperative Classification||G01N2033/0095, G01N27/002|
|European Classification||G01N27/00C, G01N27/04|
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